Gas sampling apparatus



J. D. coLLETT, JR 2,452,224

GAS SAMPLING APPARATUS FiledMay '7, 1945 2 Sheets-Sheet l firm/@NEVE J.D. COLLET-r, JR

GAS SAMPLING APPARATUS 2 Sheets-Shaet 2 Filed May '7, 1945 Patented Oct.26, 1948 orrlca I GAS SAMPLING APPARATUS James D. Collett, Jr., Houston,Tex.

Application May 7, 1945, Serial No. 592,476

4 claims. (ci. '1s-421.5)

This invention relates in general to sampling devices and moreparticularly has reference to a device for taking samples from a flowingfluid in a conduit. I

It is desirable in certain installations to obtain from a flowing streamof gas, vapor and condensate in the form of a suspension or fog arepresentative sample.

It has been found, however, that where a stream of such a mixture has asubstantial diameter the velocities at different radial distances fromthe center of the stream will .be different and the liquid contents ofsamples taken from the stream at such various different velocities willvary depending on the velocity at which the sample vis taken. It hasalso been found that if a sampling nozzle is merely placed in the streamat a given point the sample obtained will not be taken at exactly thevelocity at which the stream surrounding the nozzle is flowing unlessspecial steps are followed to insure that the sample is taken at thedesired velocity. y

The principal object of the invention is to obtain from a flowing streamof aimixture of gas, vapor and condensate in the form of suspension orfog, a representative sample,

Another object of this invention is to make it possible to take thesample from a flowing stream with the sample being taken at the samevelocity as the velocity ofstream flow adjacent the point of taking thesample.

A further object of this invention is to take a number of samples from aflowing stream which taken together will give an accurate indication ofthe liquid content of the flowing stream.

A still further object of this invention is to provide apparatus andprocedures for accomplishlng theaforesaid objects.

With these and other objects in view, the present invention resides inthe parts and combinations and steps and procedures hereinafterdescribed and illustrated. V

In order to facilitate an understanding of this invention, reference ismade to the accompanying drawings.

In the drawings:

Figure l is a vertical sectional view through one form of apparatus forcarrying out the present invention including a sampling tube andequipment for measuring the velocity of flow of fluid in the conduitfrom which the sample is taken and for measuring the velocity of flow offluid entering the `sampling tube.

Fig. 2 is a similar view of a modified form of apparatus.

Fig. 3 is a similar view of still another modified form of structure inwhich means are provided for taking a plurality of samplessimultaneously.

Fig. 4 is a sectional view taken on line 1l-:l of Fig. 3.

As shown in the drawings a flow conduitl is provided through which thestream of fluid to b sampled flows. Conduit I has been'illustrated asbeing vertical, butit, of course, may be slightly inclined relative tothe vertical although the vert tical arrangement is preferred and givesthe best pled flows downwardly through conduit l. Sampling tube 2 has anozzle 3 fitted on its open end and provided with an orifice ofpredetermined cross-sectional area.

Also within the stream at the same distance from thev center of thestream as the sampling nozzle 3 and at the same horizontal level as thesampling nozzle there is placed an impact tube l corresponding to thevelocity measuring portion of a. Pitot tube. The velocity of the flowingstream against a liquid with which this Pitot tube is filled will tendto cause the liquid to flow from the stream out through the Pitot tubeand a pressure will be generated within the Pitot tube corresponding tothe velocity of the flowing stream. The pressure exerted on the liquidin f the Pitot tube fi is measured in the vertical column or leg 5 ofsaid tube which communicates therewith by the lateral portion t,

Now it is not known at just what velocity the mixture would enter thesampling tube if the outer end were merely left open because thedifferential of pressure between the inner and outer ends of thesampling tubes might be such as to cause flow into the sampling tube atla much greater velocity thantheflow in the stream about the samplingtube. It is highly desirable that the flow into the sampling tube be atthe same velocity as that existing in the stream about the samplingtube. For the purpose of determining the velocity of the fluid enteringthe sampling tube and bringing it to the same velocity as the fluidilowing in the stream being sampled, .the sampling tube is extended tothe outside of the main conduit l and at some suitable location outsideof the main conduit is provided with a section l of the same internalcross section as the internal cross section of the orifice nozzle 3 ofthe sampling tube at itsentrance. In this portion of the sampling tubethere is placed a second impact or Pitot tube 8.' y

Tube 8 is connected at its lower end to the lower end of a vertical leg9 which is positioned in close proximity to the leg of the measuringtube l to facilitate comparison of the heights of the liquid columns inthe two legs. As illustrated. the two legs and 8 are provided withvalves I0 and II, respectively, at their upper portions and areconnected together at their upper' ends by an inverted U tube I2. At theuppermost' portion of the U- section i2 a conduit I3 is connected whichis provided with a valve I4. The conduit I3 and valves I Ii, II and Itserve to fill the legs 5 and 8 and the respective Pitot tubes 4 and 8with liquid.

'For purposes of convenience the extreme impact ends of Pitot tubes 4and 8` are at the same horizontal level so that when the flowingportions of the fluid impacting the tubes are moving at the samevelocity the level of liquids in the vmeasuring legs 5 and 9 will be atthe same level. This also facilitates the filling ofthe two tubes withliquid because as constructed liquid can be added until it overflows theimpact ends of both tubes and then both Pitot tubes will lbeautomatically filled to the same level with liquid. i

`4 or B that is connected with that leg. After the two tubes are filledwith liquid and the Vfluid to be sampled is flowing through the conduitI the level of liquid in tubes l and 8 will be depressed and the levelof liquid in tube legs 5 and 8 will rise. If the liquid in the legs land 9 come to the same level that will be an indication that thevelocities of fluid striking the ends of the two impact tubes are thesame. If this conditions exists, then the velocity of flow into thesampling tube must of necessity be the same as the velocity of ow in themain stream of fluid adjacent the sampling tube. If it be found that thelevels in the two legs of the U-tubes are not the same, then a throttlevalve I5 on the sampling tube may be opened to permit agreater velocityof flow through the sampling tube or closed to cut down on the velocityuntil the columns of liquid in the U-tube are at the same level. It isessential that the openings into the two impact tubes be at exactly thesame level.

The impact tip in the sampling tube may if desired actually be placed inthe ,intake portion of the sampling tube rather than in some remoteportion having the same cross section. In Fig. 2 of the drawingsastructure embodying this feature of the present invention is illustratedin which the impact leg 8a of the Pitot tube for measuring the velocityof flow through the sarnpling tube 2 is positioned in the elongatednozzle orice 3a. This form of the invention operates identically to thatshown in Fig. l.

In order to obtain a more representative sample 'of the fluid fiowingthrough the conduit I than could be obtained at any one point in a flowstream the present invention also contemplates the positioning of aplurality of sampling nozzles within the conduit I at various distancesfrom the center thereof. Such an arrangement is shown in Figs. 3 and 4of the drawings in which a plurality of sampling tubes 2, 2a, 2b, etc.,are

positioned with their respective nozzles at predetermined distances fromthe center of the conduit I.

In accordance with the teachings of the present invention a plurality ofimpact legs 4, 4a, 4b, etc.. of the Pitot tubes are positioned atdistances from the center of the conduit I corresponding to thedistances between said center of the conduit and the sampling nozzles ofthe conduits 2,

2a,A 2b, etc., respectively.

The desirable positions of the sampling nozzles when a plurality areemployed are midway of concentric zones of equal area. For instance, i!three nozzles are to be placed in the conduit the area of the conduitshould be divided into imaginary concentric zones, each having the samearea as each of the others. In other words, a series of imaginaryconcentric circles I6 and I1 should be drawn as illustrated in Fig. 2 ofthe drawings. The radii of these circles would be such as to divide thearea of the conduit into an inner circular zone i8. an intermediateannular zone I9 and an outer annular zone 20. Each of the three zonesI8, I9 and 20 are of equal area. After so dividing the cross-sectionalarea of the conduit 1I the sampling tubes would be positioned with thetube 2 halfway between the inner and outer peripheries of the annularzone 20, the tube 2a halfway betweenithe circles I6 and II and the tube2b halfway between the center of the conduit I and the circle I6. Ofcourse, the impact tubes 4, da and 0b would likewise be positioned atdistances relative to the imaginary circles and center of the conduit Icorresponding to the positioning of the nozzle ends of the impact tubes.

Each of the tubes 2a, 2b, 4a and 4b are connected with equipmentidentical to that shown associated with the tubes 2 and 4 in Fig.` 3.The details of this showing have been omitted to simplify theillustration of the invention in the drawings.

With the structure more or less diagrammatically illustrated in Figs. 3and 4 of the drawings,

a plurality of samples which would give a more accurate representationof the cross section of the stream of fluid flowing through the conduitI can be obtained.

From the foregoing description it will be appreciated that the presentinvention provides novel methods and equipment for obtaining samples offluid from a flowing stream thereof.

Having described my invention, I claim:

1. In an apparatus for taking samples of a uid flowing through aconduit, a sampling nozzle disposed in said conduit and provided with anintake orifice facing upstream and positioned a'predetermined distancefrom thecenter ol' said conduit, a. Pitot tube having its impactreceiving end facing upstream and positioned from the center of saidconduit a distance equal to that at which the nozzle orifice is spaced.and a second Pitot tube having its impact receiving end disposed in saidnozzle and facing upstream. said Pitot tubes having measuring columnsdisposed in juxtaposed parallel relation and having their impact facesdisposed' at the same horizontal level.

2. In an apparatus for taking samples of a fluid flowing through aconduit, a sampling nozzle disposed in said conduit and provided with anintake orifice facing upstream and positioned a predetermined distancefrom the center of said conduit. a, Pitot tube having its impactreceiving end facing upstream and positioned from. the center of -saidconduit a distance equal to that at which the nozzle orifice is spaced.a pipe connected to said Pitot tubes having measuring columns disposedin juxtaposed parallel relation and having their impact faces disposedat the same horizontal level.

3. In an apparatus for taking samples of a iiuid flowing downwardlythrough a vertically extending conduit,y a sampling lnozzle disposed insaid conduit and provided with an intake orice facing upstream andpositioned a predetermined distance from the center of said conduit, aPitot tube having its impact receiving end facing upstream andpositioned from the center of said conduit a distance equal to that atwhich the nozzle orifice is spaced, and a second Pitot tube having itsimpact receiving end disposed in said nozzle and facing upstream, saidPitot tubes having measuring columns disposed in juxtaposed parallelrelation and having their impact faces disposed at the same horizontallevel.

4. In an apparatus for taking samples of a fluid owing .downwardlythrough a vertically extending conduit, a sampling nozzle disposed insaid conduit and provided with an intake orifice facing upstream andpositioned a predetermined distance from the center of said conduit, aPitot tube having its impact receiving end facing upstream andpositioned from the center of said conduit 6 a distance equal to that atwhich the nozzle orifice is spaced, a second Pitot tube havingV itsimpact receiving end disposed in said nozzle and facing upstream, saidPitot tubes having measuring coli umns disposed in juxtaposed parallelrelation and having their impact faces disposed at the same Yhorizontallevel, and means common to said Pitot tubes for filling them withmeasuring liquid.

JAMES D. COLLETT, Jn.

REFERENCES CITED The following references arev of record in the ile ofthis patent:

UNITED STATES PATENTS Number Name Date 1,100,171 Brown June 16, 19141,364,035 Carter Dec. 28, 1920 2,030,682 Campbell Feb. 11, 19362,245,679 Kelley June 17, 1941 2,363,625 Swearingen Nov. 28, 19442,423,394 Lee July 1, 1947 FOREIGN PATENTS Number Country Date 469,665Germany Dec. 20, 1928 OTHER REFERENCES Brady et al., J. Ind. and Eng.Chem., 3, 662, 670

Place, The Chemist Analyst, 19, January 1, 1930, pages 17 and 18.

